runtime-rs: Introduce qemu-rs vfio device hotplug handler

This commit note that the current implementation restriction where
'multifunction=on' is temporarily unsupported. While the feature
isn't available in the present version, we explicitly acknowledge
this limitation and commit to addressing it in future iterations
to enhance functional completeness.

Tracking issue #11292 has been created to monitor progress towards
full multifunction support.

Fixes #10361

Signed-off-by: alex.lyn <alex.lyn@antgroup.com>

src/runtime-rs/crates/hypervisor/src/qemu/inner.rs

@@ -632,6 +632,25 @@ impl QemuInner {
 
                 return Ok(DeviceType::Block(block_device));
             }
+            DeviceType::Vfio(mut vfiodev) => {
+                // FIXME: the first one might not the true device we want to passthrough.
+                // The `multifunction=on` is temporarily unsupported.
+                // Tracking issue #11292 has been created to monitor progress towards full multifunction support.
+                let primary_device = vfiodev.devices.first_mut().unwrap();
+                info!(
+                    sl!(),
+                    "qmp hotplug vfio primary_device {:?}", &primary_device
+                );
+
+                primary_device.guest_pci_path = qmp.hotplug_vfio_device(
+                    &primary_device.hostdev_id,
+                    &primary_device.bus_slot_func,
+                    &vfiodev.driver_type,
+                    &vfiodev.bus,
+                )?;
+
+                return Ok(DeviceType::Vfio(vfiodev));
+            }
             _ => info!(sl!(), "hotplugging of {:#?} is unsupported", device),
         }
         Ok(device)

src/runtime-rs/crates/hypervisor/src/qemu/qmp.rs

@@ -596,6 +596,42 @@ impl Qmp {
 
         Ok(Some(pci_path))
     }
+
+    pub fn hotplug_vfio_device(
+        &mut self,
+        hostdev_id: &str,
+        bus_slot_func: &str,
+        driver: &str,
+        bus: &str,
+    ) -> Result<Option<PciPath>> {
+        let mut vfio_args = Dictionary::new();
+        let bdf = if !bus_slot_func.starts_with("0000") {
+            format!("0000:{}", bus_slot_func)
+        } else {
+            bus_slot_func.to_owned()
+        };
+        vfio_args.insert("addr".to_owned(), "0x0".into());
+        vfio_args.insert("host".to_owned(), bdf.into());
+        vfio_args.insert("multifunction".to_owned(), "off".into());
+
+        let vfio_device_add = qmp::device_add {
+            driver: driver.to_string(),
+            bus: Some(bus.to_string()),
+            id: Some(hostdev_id.to_string()),
+            arguments: vfio_args,
+        };
+        info!(sl!(), "vfio_device_add: {:?}", vfio_device_add.clone());
+
+        self.qmp
+            .execute(&vfio_device_add)
+            .map_err(|e| anyhow!("device_add vfio device failed {:?}", e))?;
+
+        let pci_path = self
+            .get_device_by_qdev_id(hostdev_id)
+            .context("get device by qdev_id failed")?;
+
+        Ok(Some(pci_path))
+    }
 }
 
 fn vcpu_id_from_core_id(core_id: i64) -> String {